The proposed research lies in 4 related areas: (1) The CD spectra of key synthetic polynucleotides will be studied to add to our growing library of spectra for use in spectral analyses of natural DNAs. Of special importance will be a study of mixtures of poly(d(A-G)), and poly(d(C-T)) single strands, to determine under what conditions self-complexes or multiple-stranded forms may exist. (2) The ethanol-induced B to A conformational transition will be studied for various synthetic DNA sequences to determine whether complex sequences might exhibit conformational heterogeneity in solution. (3) In preliminary work, we have found that DNA molecules can be condensed in the presence of salt and ethanol to give a novel compact array that shows differential light scattering. This ethanol- and salt-condensed DNA will be investigated by combined circular dichroism and electron microscopic measurements, as well as by other techniques. (4) The complexes formed between the gene 5 protein of fd phage and various DNAs will be characterized by their CD spectra under conditions similar to those used for structural studies by X-ray diffraction.